It would be kind cool to fight against other spartans or marines in H6’s campaign. I remember me and my brother would mess around in H4 in that mission where Lasky gives you the Pelican to stop the Didact. We would kill the marines and spartans, good times. But there would have to be a reason for the marines/spartans to attack you right? Just a thought I had
They had that chance in Halo 5, but ruined it. I do not see any reason currently why they would do it in Halo 6.